SLEEP

Meaning of sleep 

Sleep is a state in which an organism enters of a period of time, which is characterized by reduced awareness, body movement and metabolic activity.

Sleep is slightly different from other sleeplike states like hibernation or coma. The reason for is because sleep can be interrupted by a loud, by touching or hitting the subject and by change in temperature. 

The interruption of sleep in human and other mammals is marked by a change (I).

During sleep most animals close their eyes
and most of their systems are in an anabolic state which helps to restore the immune, nervous, muscular, skeletal and other system in the body.

All mammal and bird have been confirmed to sleep but reptiles, fish, and other life from have not been confirmed by scientist to sleep. It has also been proven that larger animal sleep less than smaller animals.

Types of sleep

There are two types of sleep which are RAPID EYES MOVEMENT (REM) and NON RAPID EYES MOVEMENT (NREM) sleep. 

RAPID EYES MOVEMENT (REM) sleep is characterized by short, rapid wave patters similar to brain wave activity of the waking state. When subject were awakened during REM sleep, they reported vivid dream (mostly in children) i.e. say out what was going on in their dreams. Scientists believe that REM sleep is closely related to wakefulness. Dreams or (night mares) also occur during REM sleep.

ALSO READ :WHY SLEEP IS IMPORTANT

NON RAPID EYES MOVEMENT (NREM) sleep is characterized by reduction in metabolism, heart and breathing rate, blood pressure and body temperature. It is considered to be deep sleep (the deepest part of NREM is called slow wave sleep).

When awakened from NREM sleep, subjects are much less likely to report vivid, action packed dreams. NREM sleep is dominated by large slow waves that contrast markedly to the short, rapid wave patterns characteristic of REM sleep and the waking state.

Sleep cycle

Sleep studies have shown that during a normal night sleep occurs in cycles of approximately 90 minutes. This cycle is called ultradian sleep cycle. The number of REM periods varies from 4-6 depending on the length of the episodes and the total time asleep. REM sleep can last of about 10 minutes in the beginning of the night and during the night can increase to about 30 minutes and in early hours of the morning, most adult send 20% of their total sleep in REM sleep.